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Critical Reviews in Toxicology Oct 2014Abstract Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods,... (Review)
Review
Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts.
Abstract Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007) . Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of "total Al"assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al(+3) to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)(+2) and Al(H2O)6 (+3)] that after complexation with O2(•-), generate Al superoxides [Al(O2(•))](H2O5)](+2). Semireduced AlO2(•) radicals deplete mitochondrial Fe and promote generation of H2O2, O2 (•-) and OH(•). Thus, it is the Al(+3)-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer's disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances.
Topics: Aluminum; Aluminum Hydroxide; Aluminum Oxide; Animals; Carcinogenesis; Cardiovascular System; Central Nervous System; Disease Models, Animal; Dose-Response Relationship, Drug; Endocrine System; Europe; Gastrointestinal Tract; Guidelines as Topic; Humans; Kidney; Liver; Nanoparticles; Occupational Exposure; Randomized Controlled Trials as Topic; Respiratory System; Risk Assessment; Risk Factors
PubMed: 25233067
DOI: 10.3109/10408444.2014.934439 -
The Cochrane Database of Systematic... May 2018In children, dental caries (tooth decay) is among the most prevalent chronic diseases worldwide. Pulp interventions are indicated for extensive tooth decay. Depending on... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
In children, dental caries (tooth decay) is among the most prevalent chronic diseases worldwide. Pulp interventions are indicated for extensive tooth decay. Depending on the severity of the disease, three pulp treatment techniques are available: direct pulp capping, pulpotomy and pulpectomy. After treatment, the cavity is filled with a medicament. Materials commonly used include mineral trioxide aggregate (MTA), calcium hydroxide, formocresol or ferric sulphate.This is an update of a Cochrane Review published in 2014 when insufficient evidence was found to clearly identify one superior pulpotomy medicament and technique.
OBJECTIVES
To assess the effects of different pulp treatment techniques and associated medicaments for the treatment of extensive decay in primary teeth.
SEARCH METHODS
Cochrane Oral Health's Information Specialist searched the Cochrane Oral Health Group's Trials Register (to 10 August 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2017, Issue 7), MEDLINE Ovid (1946 to 10 August 2017), Embase Ovid (1980 to 10 August 2017) and the Web of Science (1945 to 10 August 2017). OpenGrey was searched for grey literature. The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases.
SELECTION CRITERIA
We included randomised controlled trials (RCTs) comparing interventions that combined a pulp treatment technique with a medicament or device in children with extensive decay in the dental pulp of their primary teeth.
DATA COLLECTION AND ANALYSIS
Two review authors independently extracted data and assessed 'Risk of bias'. We contacted authors of RCTs for additional information when necessary. The primary outcomes were clinical failure and radiological failure, as defined in trials, at six, 12 and 24 months. We performed data synthesis with pair-wise meta-analyses using fixed-effect models. We assessed statistical heterogeneity by using I² coefficients.
MAIN RESULTS
We included 40 new trials bringing the total to 87 included trials (7140 randomised teeth) for this update. All were small, single-centre trials (median number of randomised teeth = 68). All trials were assessed at unclear or high risk of bias.The 87 trials examined 125 different comparisons: 75 comparisons of different medicaments or techniques for pulpotomy; 25 comparisons of different medicaments for pulpectomy; four comparisons of pulpotomy and pulpectomy; and 21 comparisons of different medicaments for direct pulp capping.The proportion of clinical failures and radiological failures was low in all trials. In many trials, there were either no clinical failures or no radiographic failures in either study arm.For pulpotomy, we assessed three comparisons as providing moderate-quality evidence. Compared with formocresol, MTA reduced both clinical and radiological failures, with a statistically significant difference at 12 months for clinical failure and at six, 12 and 24 months for radiological failure (12 trials, 740 participants). Compared with calcium hydroxide, MTA reduced both clinical and radiological failures, with statistically significant differences for clinical failure at 12 and 24 months. MTA also appeared to reduce radiological failure at six, 12 and 24 months (four trials, 150 participants) (low-quality evidence). When comparing calcium hydroxide with formocresol, there was a statistically significant difference in favour of formocresol for clinical failure at six and 12 months and radiological failure at six, 12 and 24 months (six trials (one with no failures), 332 participants).Regarding pulpectomy, we found moderate-quality evidence for two comparisons. The comparison between Metapex and zinc oxide and eugenol (ZOE) paste was inconclusive, with no clear evidence of a difference between the interventions for failure at 6 or 12 months (two trials, 62 participants). Similarly inconclusive, there was no clear evidence of a difference in failure between Endoflas and ZOE (outcomes measured at 6 months; two trials, 80 participants). There was low-quality evidence of a difference in failure at 12 months that suggested ZOE paste may be better than Vitapex (calcium hydroxide/iodoform) paste (two trials, 161 participants).Regarding direct pulp capping, the small number of studies undertaking the same comparison limits any interpretation. We assessed the quality of the evidence as low or very low for all comparisons. One trial appeared to favour formocresol over calcium hydroxide; however, there are safety concerns about formocresol.
AUTHORS' CONCLUSIONS
Pulp treatment for extensive decay in primary teeth is generally successful. Many included trials had no clinical or radiological failures in either trial arm, and the overall proportion of failures was low. Any future trials in this area would require a very large sample size and follow up of a minimum of one year.The evidence suggests MTA may be the most efficacious medicament to heal the root pulp after pulpotomy of a deciduous tooth. As MTA is relatively expensive, future research could be undertaken to confirm if Biodentine, enamel matrix derivative, laser treatment or Ankaferd Blood Stopper are acceptable second choices, and whether, where none of these treatments can be used, application of sodium hypochlorite is the safest option. Formocresol, though effective, has known concerns about toxicity.Regarding pulpectomy, there is no conclusive evidence that one medicament or technique is superior to another, and so the choice of medicament remains at the clinician's discretion. Research could be undertaken to confirm if ZOE paste is more effective than Vitapex and to evaluate other alternatives.Regarding direct pulp capping, the small number of studies and low quality of the evidence limited interpretation. Formocresol may be more successful than calcium hydroxide; however, given its toxicity, any future research should focus on alternatives.
Topics: Aluminum Compounds; Calcium Compounds; Calcium Hydroxide; Child; Child, Preschool; Controlled Clinical Trials as Topic; Dental Caries; Dental Cements; Dental Materials; Drug Combinations; Electric Stimulation Therapy; Ferric Compounds; Formocresols; Humans; Molar; Oxides; Pulpectomy; Pulpotomy; Randomized Controlled Trials as Topic; Silicates; Tooth, Deciduous; Treatment Failure; Zinc Oxide-Eugenol Cement
PubMed: 29852056
DOI: 10.1002/14651858.CD003220.pub3 -
The International Journal of... 2016The aim of this study was to perform a systematic review and meta-analysis based on clinical trials that evaluated the main outcomes of glass-ceramic and feldspathic... (Meta-Analysis)
Meta-Analysis Review
PURPOSE
The aim of this study was to perform a systematic review and meta-analysis based on clinical trials that evaluated the main outcomes of glass-ceramic and feldspathic porcelain laminate veneers.
MATERIALS AND METHODS
A systematic search was carried out in Cochrane and PubMed databases. From the selected studies, the survival rates for porcelain and glass-ceramic veneers were extracted, as were complication rates of clinical outcomes: debonding, fracture/chipping, secondary caries, endodontic problems, severe marginal discoloration, and influence of incisal coverage and enamel/dentin preparation. The Cochran Q test and the I(2) statistic were used to evaluate heterogeneity.
RESULTS
Out of the 899 articles initially identified, 13 were included for analysis. Metaregression analysis showed that the types of ceramics and follow-up periods had no influence on failure rate. The estimated overall cumulative survival rate was 89% (95% CI: 84% to 94%) in a median follow-up period of 9 years. The estimated survival for glass-ceramic was 94% (95% CI: 87% to 100%), and for feldspathic porcelain veneers, 87% (95% CI: 82% to 93%). The meta-analysis showed rates for the following events: debonding: 2% (95% CI: 1% to 4%); fracture/chipping: 4% (95% CI: 3% to 6%); secondary caries: 1% (95% CI: 0% to 3%); severe marginal discoloration: 2% (95% CI: 1% to 10%); endodontic problems: 2% (95% CI: 1% to 3%); and incisal coverage odds ratio: 1.25 (95% CI: 0.33 to 4.73). It was not possible to perform meta-analysis of the influence of enamel/dentin preparation on failure rates.
CONCLUSION
Glass-ceramic and porcelain laminate veneers have high survival rates. Fracture/ chipping was the most frequent complication, providing evidence that ceramic veneers are a safe treatment option that preserve tooth structure.
Topics: Aluminum Silicates; Ceramics; Dental Porcelain; Dental Restoration Failure; Dental Veneers; Humans; Potassium Compounds; Surface Properties; Survival Analysis; Treatment Outcome
PubMed: 26757327
DOI: 10.11607/ijp.4315 -
The Journal of Prosthetic Dentistry Jun 2019Veneer chipping and crown decementation are the most frequent failures in restorations using zirconia as an infrastructure. Increasing the roughness of the zirconia... (Meta-Analysis)
Meta-Analysis Review
Evaluation of zirconia surface roughness after aluminum oxide airborne-particle abrasion and the erbium-YAG, neodymium-doped YAG, or CO lasers: A systematic review and meta-analysis.
STATEMENT OF PROBLEM
Veneer chipping and crown decementation are the most frequent failures in restorations using zirconia as an infrastructure. Increasing the roughness of the zirconia surface has been suggested to address this problem.
PURPOSE
The purpose of this systematic review and meta-analysis was to evaluate yttria-stabilized tetragonal zirconia polycrystal surface roughness, produced with aluminum oxide airborne-particle abrasion and the erbium yttrium aluminum garnet (YAG), neodymium-doped YAG, or CO lasers.
MATERIAL AND METHODS
This study was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. The review identified relevant studies through December 2017 with no limit on the publication year in the search databases: Web of Science, Scopus, and MEDLINE via PubMed. The selected studies were submitted to a risk of bias assessment. The means and standard deviations of roughness were evaluated for the meta-analysis using Review Manager software.
RESULTS
The 17 studies that met all inclusion criteria presented a medium risk of bias. All the treatment methods tested were able to create a roughness on the yttria-stabilized tetragonal zirconia polycrystal surface. The I test values presented a high heterogeneity among the studies.
CONCLUSIONS
The presintered specimens submitted to airborne-particle abrasion had higher surface roughness compared with abrasion after the sintering process. Irradiation with the neodymium-doped YAG and CO lasers was destructive to the zirconia surfaces. The erbium laser used with lower energy intensity appears to be a promising method for surface treatment.
Topics: Aluminum; Aluminum Oxide; Carbon Dioxide; Erbium; Lasers, Solid-State; Materials Testing; Neodymium; Surface Properties; Yttrium; Zirconium
PubMed: 30711290
DOI: 10.1016/j.prosdent.2018.07.001 -
Operative Dentistry Jan 2021The literature reviewed suggests that airborne particle abrasion has no negative effects on the bond strength of resin-based materials to dentin and that a positive... (Meta-Analysis)
Meta-Analysis
CLINICAL RELEVANCE
The literature reviewed suggests that airborne particle abrasion has no negative effects on the bond strength of resin-based materials to dentin and that a positive influence on dentin bond strength was only achieved in specific air-abrasion conditions.
SUMMARY
In this systematic review the authors investigated how airborne-particle abrasion (APA) using aluminum oxide affects the bond strength of resin-based materials to dentin. The search was performed in three databases. In vitro studies (Type of study) comparing the bond strength of resin-based materials (Outcome) to air-abraded (Intervention) compared with non-air-abraded (Comparison) human dentin (Population) were included (the PICOT elements are given parenthetically). From 5437 unique articles, 65 were read in full, 33 were included in the qualitative synthesis, and 32 were included in the meta-analysis. Methodologic quality and risk of bias were assessed. Comparisons were performed between air-abraded and control dentin groups by adopting a random-effects model (α=0.05). Additional analyses were carried out for the different parameters used in APA: type of surface treatment in the control group, particle size, air pressure, and APA duration. The bond strength to air-abraded dentin was favored only when the control surface was treated with a hand excavator. For particle size, APA was favored when the particle size was >30 μm and the controls were no treatment or hand excavator or when the particle size was ≤30 μm and the control was bur. In addition, the results favored air-abraded groups only when the pressure was > 5 bar and bur was used in the control group. No significant differences were observed for duration of APA. No comparison on bond strength considering the presence of aging conditions was possible in the included studies due to the low number of studies that aged the specimens. In conclusion, APA had no negative effects on the bond strength of resin-based materials to dentin and was able to improve the dentin bond strength only when the particle size was > 30 μm and air pressure was > 5 bar. PROSPERO registration protocol: CRD42018096128.
Topics: Aged; Aluminum Oxide; Composite Resins; Dental Bonding; Dentin; Humans; Materials Testing; Resin Cements; Shear Strength; Surface Properties
PubMed: 32926155
DOI: 10.2341/19-216-L -
Clinical Oral Investigations Sep 2023The aim of this systematic review and meta-analysis is to assess the comparative clinical success and survival of intracoronal indirect restorations using gold, lithium... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVES
The aim of this systematic review and meta-analysis is to assess the comparative clinical success and survival of intracoronal indirect restorations using gold, lithium disilicate, leucite, and indirect composite materials.
MATERIAL AND METHODS
This systematic review and meta-analysis were conducted following the Cochrane Handbook for Systematic Reviews of Interventions and PRISMA guidelines. The protocol for this study was registered in PROSPERO (registration number: CRD42021233185). A comprehensive literature search was conducted across various databases and sources, including PubMed/Medline, Embase, Cochrane Library, Web of Science, ClinicalTrials.gov, and gray literature. A total of 7826 articles were screened on title and abstract. Articles were not excluded based on the vitality of teeth, the language of the study, or the observation period. The risk difference was utilized for the analyses, and a random-effects model was applied. All analyses were conducted with a 95% confidence interval (95% CI). The calculated risk differences were derived from the combined data on restoration survival and failures obtained from each individual article. The presence of heterogeneity was assessed using the I statistic, and if present, the heterogeneity of the data in the articles was evaluated using the non-parametric chi-squared statistic (p < 0.05).
RESULTS
A total of 12 eligible studies were selected, which included 946 restorations evaluated over a minimum observation period of 1 year and a maximum observation period of 7 years. Results of the meta-analysis indicated that intracoronal indirect resin composite restorations have an 18% higher rate of failure when compared to intracoronal gold restorations over 5-7 years of clinical service (risk difference = - 0.18 [95% CI: - 0.27, - 0.09]; p = .0002; I = 0%). The meta-analysis examining the disparity in survival rates between intracoronal gold and leucite restorations could not be carried out due to methodological differences in the studies.
CONCLUSIONS
According to the currently available evidence, medium-quality data indicates that lithium disilicate and indirect composite materials demonstrate comparable survival rates in short-term follow-up. Furthermore, intracoronal gold restorations showed significantly higher survival rates, making them a preferred option over intracoronal indirect resin-composite restorations. Besides that, the analysis revealed no statistically significant difference in survival rates between leucite and indirect composite restorations. The short observation period, limited number of eligible articles, and low sample size of the included studies were significant limitations.
CLINICAL SIGNIFICANCE
Bearing in mind the limitations of the reviewed literature, this systematic review and meta-analysis help clinicians make evidence-based decisions on how to restore biomechanically compromised posterior teeth.
Topics: Dental Porcelain; Aluminum Silicates; Composite Resins; Gold
PubMed: 37597003
DOI: 10.1007/s00784-023-05050-x -
Pediatric Dentistry Nov 2023to update the 2016 systematic review evidence for vital pulp therapy (VPT) for primary teeth affected by caries or trauma. The population, intervention, comparison,... (Meta-Analysis)
Meta-Analysis
to update the 2016 systematic review evidence for vital pulp therapy (VPT) for primary teeth affected by caries or trauma. The population, intervention, comparison, outcomes, and study (PICOS) design inclusion/exclusion was used for multiple databases. Risk of bias, meta-analyses using RevMan, and certainty of evidence was created. A total of 299 studies were included; no trauma was found. Indirect pulp treatment (IPT) resulted in 97 percent success. Two calcium silicate cement (CSC) pulpotomies' success using mineral trioxide aggregate (MTA) and Biodentine were 94 percent and 90 percent, respectively, greater than for direct pulp capping (DPC; 86 percent) and other pulpotomies (moderate certainty). The success of IPT versus pulpotomy at 24 months showed no significant difference (P=0.31). Different liners or capping agents did not affect the success of IPT (P=0.79) or DPC at 24 months (P=0.24). The two CSC pulpotomies were not significantly different based on 24-month success (P=0.34). The formocresol pulpotomy success at 24 months was significantly lower than for MTA (P=0.02). Ferric sulfate had a significant lower success at 24 months than MTA pulpotomy (69 percent versus 92 percent; P=0.03). Zinc oxide eugenol, as a singular pulpotomy, had low success (65 percent). Selective/stepwise caries removal did significantly better at avoiding pulp exposures than complete excavation (P<0.001). Complete, selective, and no caries removal (Hall technique [HT], steel crown placement with no caries removal) had no significant difference in pulp vitality success for deep caries at 24 months (P=0.29). For deep caries affecting vital incisors, pulpotomy had significantly greater success than pulpectomy (P=0.002). The following had no significant effect on MTA pulpotomy success: coronal pulp removal methods; irrigation solution; method to control hemorrhage; base over MTA; treatment in one or two visits; and anterior or posterior teeth. Vital pulp therapy success of indirect pulp treatment or two calcium silicate cement pulpotomies demonstrated improved success over direct pulp capping and other pulpotomies based on 24-month evidence with moderate certainty. The Hall technique did not significantly reduce pulp vitality success versus caries removal.
Topics: Humans; Calcium Compounds; Silicates; Dental Care; Dental Cements; Zinc Oxide-Eugenol Cement; Dental Pulp Capping; Pulpotomy; Glass Ionomer Cements; Tooth, Deciduous; Oxides; Drug Combinations; Treatment Outcome; Aluminum Compounds
PubMed: 38129755
DOI: No ID Found -
The Japanese Dental Science Review Dec 2023The use of graphecs excellent mechanical properties. However, it is necessary to evaluate the biological effects of this material. This systematic review aimed to... (Review)
Review
The use of graphecs excellent mechanical properties. However, it is necessary to evaluate the biological effects of this material. This systematic review aimed to observe and understand through studies the current state of the art regarding osseointegration, antimicrobial capacity, and the cytotoxicity of graphene coating applied to the surface of dental implant materials. Searches in PubMed, Embase, Science Direct, Web of Science, and Google Scholar databases were conducted between June and July 2021 and updated in May 2022 using the keywords: graphene, graphene oxide, dental implants, zirconium, titanium, peek, aluminum, disilicate, methyl-methacrylate, cytotoxicity, osseointegration, and bone regeneration. The criteria included in vivo and in vitro studies that evaluated antimicrobial capacity and/or osseointegration and/or cytotoxicity of dental implant materials coated with graphene compounds. The risk of bias for in vitro studies was assessed by the JBI tool, and for in vivo studies, Syrcle's risk of bias tool for animal studies was used. The database search resulted in 176 articles. Of the 18 articles selected for full reading, 16 remained in this systematic review. The use of graphene compounds as coatings on the surface of implant materials is promising because it promotes osseointegration and has antimicrobial capacity. However, further studies are needed to ensure its cytotoxic potential.
PubMed: 37680613
DOI: 10.1016/j.jdsr.2023.08.005 -
Clinical Oral Implants Research Sep 2023In patients with dental implants, what is the effect of transmucosal components made of materials other than titanium (alloys) compared to titanium (alloys) on the... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVES
In patients with dental implants, what is the effect of transmucosal components made of materials other than titanium (alloys) compared to titanium (alloys) on the surrounding peri-implant tissues after at least 1 year?
MATERIALS AND METHODS
This systematic review included eligible randomized controlled trials identified through an electronic search (Medline, Embase and Web of Science) comparing alternative abutment materials versus titanium (alloy) abutments with a minimum follow-up of 1 year and including at least 10 patients/group. Primary outcomes were peri-implant marginal bone level (MBL) and probing depth (PD), these were evaluated based on meta-analyses. Abutment survival, biological and technical complications and aesthetic outcomes were the secondary outcomes. The risk of bias was assessed with the RoB2-tool. This review is registered in PROSPERO with the number (CRD42022376487).
RESULTS
From 5129 titles, 580 abstracts were selected, and 111 full-text articles were screened. Finally, 12 articles could be included. Concerning the primary outcomes (MBL and PD), no differences could be seen between titanium abutment and zirconia or alumina abutments, not after 1 year (MBL: zirconia: MD = -0.24, 95% CI: -0.65 to 0.16, alumina: MD = -0.06, 95% CI: -0.29 to 0.17) (PD: zirconia: MD = -0.06, 95% CI: -0.41 to 0.30, alumina: MD = -0.29, 95% CI: -0.96 to 0.38), nor after 5 years. Additionally, no differences were found concerning the biological complications and aesthetic outcomes. The most important technical finding was abutment fracture in the ceramic group and chipping of the veneering material.
CONCLUSIONS
Biologically, titanium and zirconia abutments seem to function equally up to 5 years after placement.
Topics: Humans; Titanium; Dental Implants; Alloys; Aluminum Oxide
PubMed: 37750527
DOI: 10.1111/clr.14159 -
The Annals of Occupational Hygiene Oct 2016Engineered nanomaterials (ENMs) have a large economic impact in a range of fields, but the concerns about health and safety of occupational activities involving... (Review)
Review
BACKGROUND
Engineered nanomaterials (ENMs) have a large economic impact in a range of fields, but the concerns about health and safety of occupational activities involving nanomaterials have not yet been addressed. Monitoring exposure is an important step in risk management. Hence, the interest for reviewing studies that reported a potential for occupational exposure.
METHODS
We systematically searched for studies published between January 2000 and January 2015. We included studies that used a comprehensive method of exposure assessment. Studies were grouped by nanomaterial and categorized as carbonaceous, metallic, or nanoclays. We summarized data on task, monitoring strategy, exposure outcomes, and controls in a narrative way. For each study, the strength of the exposure assessment was evaluated using predetermined criteria. Then, we identified all exposure situations that reported potential occupational exposure based on qualitative or quantitative outcomes. Results were synthesized and general conclusion statements on exposure situations were formulated. The quality of evidence for the conclusion statements was rated as low, moderate, or high depending on the number of confirmed exposure situations, the strength of the exposure assessment, and the consistency of the results.
RESULTS
From the 6403 references initially identified, 220 were selected for full-text screening. From these, 50 studies describing 306 exposure situations in 72 workplaces were eligible for inclusion (27 industrial-scale plants and 45 research or pilot-scale units). There was a potential for exposure to ENMs in 233 of the exposure situations. Exposure occurred in 83% (N = 107) of the situations with carbonaceous ENMs, in 73% (N = 120) of those with metallic ENMs and in 100% (N = 6) of those with nanoclay. Concentrations of elemental carbon in the workers' breathing zone ranged from not detected (ND) to 910 µg m(-3) with local engineering controls (LEC), and from ND to 1000 µg m(-3) without those controls. For carbon nanofibres (CNFs), particle counts ranged from ND to 1.61 CNF structures cm(-3) with LEC, and from 0.09 to 193 CNF structures cm(-3) without those controls. The mass concentrations of aluminium oxide, titanium dioxide, silver, and iron nanoparticles (NPs) were ND, 10-150, 0.24-0.43, and 32 µg m(-3) with LEC, while they were <0.35, non-applicable, 0.09-33, and 335 µg m(-3) without those controls, respectively.
CONCLUSIONS
Regarding the potential of exposure in the workplace, we found high-quality evidence for multiwalled carbon nanotubes (CNTs), single-walled CNTs, CNFs, aluminium oxide, titanium dioxide, and silver NPs; moderate-quality evidence for non-classified CNTs, nanoclays, and iron and silicon dioxide NPs; low-quality evidence for fullerene C60, double-walled CNTs, and zinc oxide NPs; and no evidence for cerium oxide NPs. We found high-quality evidence that potential exposure is most frequently due to handling tasks, that workers are mostly exposed to micro-sized agglomerated NPs, and that engineering controls considerably reduce workers' exposure. There was moderate-quality evidence that workers are exposed in secondary manufacturing industrial-scale plants. There was low-quality evidence that workers are exposed to airborne particles with a size <100nm. There were no studies conducted in low- and middle-income countries.
Topics: Air Pollutants, Occupational; Environmental Monitoring; Humans; Inhalation Exposure; Nanotubes, Carbon; Occupational Exposure; Particle Size; Risk Assessment
PubMed: 27422281
DOI: 10.1093/annhyg/mew041